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Main Idea and Its Support is a free printable Grade 4 English worksheet on working out a main idea from the details that support it, aligned to Common Core standard RI.4.2. It prints 8 questions with an answer key on its own sheet of paper, in 25 versions that each ask different questions, so no two students in the class work from the same page. Print it from the browser or download it as a PDF — no account, no email.

Set 17 of 25 · the same problems every time you open this link.

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Set 1 has all 25 in a single PDF. All 25 sets ask different questions.

Main Idea and Its Support

RI.4.2

NameDate

Circle the right answer.

1.A paragraph says: some volcanoes pour out rivers of lava; others explode in clouds of ash; some have been quiet for thousands of years. What is its main idea?
  • A.Ash is gray.
  • B.Lava is hot.
  • C.Volcanoes behave in different ways.
2.A paragraph says: earthworms tunnel through soil and let air in; they drag dead leaves underground; their waste makes the soil richer. What is its main idea?
  • A.Earthworms live underground.
  • B.Earthworms help keep soil healthy.
  • C.Leaves fall in the fall.
3.A paragraph says: coral reefs cover a tiny part of the sea floor; a quarter of all sea creatures live on them; many fish lay their eggs there. What is its main idea?
  • A.Coral reefs are very small.
  • B.Coral reefs are home to a great deal of sea life.
  • C.Fish lay eggs.
4.A paragraph says: early phones were fixed to the wall; later phones had no cord; today's phones fit in a pocket and take photos. What is its main idea?
  • A.Telephones have changed a great deal over time.
  • B.Walls hold phones.
  • C.Phones take photos.
5.A paragraph says: libraries lend books for free; many offer computers anyone can use; they run reading clubs for children. What is its main idea?
  • A.Libraries offer many free services to a town.
  • B.Computers are useful.
  • C.Children like clubs.
6.A paragraph says: Roman roads ran straight for miles; they were laid in layers so water drained away; some are still used today. What is its main idea?
  • A.Roman roads were built to last.
  • B.Romans liked straight lines.
  • C.Water drains away.
7.A paragraph says: Fleming saw mold kill germs; Florey and Chain found a way to make it in large amounts; by 1944 it was treating soldiers. What is its main idea?
  • A.Soldiers were wounded in 1944.
  • B.Mold grows in dishes.
  • C.Making penicillin into a medicine took the work of many people.
8.A paragraph says: lighthouses warn ships away from rocks; each one flashes its own pattern; sailors use the pattern to tell where they are. What is its main idea?
  • A.Lights can flash.
  • B.Rocks are dangerous.
  • C.Lighthouses keep ships safe and help them find their way.

LessonPrint · RI.4.2 · Set 17 · free to copy for classroom use

Answer key — Main Idea and Its Support

Set 17. Prints on its own sheet.

  1. 1.Volcanoes behave in different ways.
  2. 2.Earthworms help keep soil healthy.
  3. 3.Coral reefs are home to a great deal of sea life.
  4. 4.Telephones have changed a great deal over time.
  5. 5.Libraries offer many free services to a town.
  6. 6.Roman roads were built to last.
  7. 7.Making penicillin into a medicine took the work of many people.
  8. 8.Lighthouses keep ships safe and help them find their way.

More practice for RI.4.2

State the main idea, show the details behind it, and summarize.

Teaching this next? The Main Idea and a Summary is the 40-minute plan for it, with the misconceptions to expect.

All Grade 4 worksheets

Last reviewed 2026-09-05. Aligned to RI.4.2 of the Common Core State Standards for English Language Arts.